Data from: Quantifying the effects of migration and mutation on adaptation and demography in spatially heterogeneous environments

AbstractHow do mutation and gene flow influence population persistence, niche expansion, and local adaptation in spatially heterogeneous environments? In this article, we analyse a demographic and evolutionary model of adaptation to an environment containing two habitats in equal frequencies, and we bridge the gap between different theoretical frameworks. Qualitatively, our model yields four qualitative types of outcomes: (i) global extinction of the population (ii) adaptation to one habitat only, but also adaptation to both habitats with (iii) specialized phenotypes, or (iv) with generalized phenotypes; and we determine the conditions under which each equilibrium is reached. We derive new analytical approximations for the local densities and the distributions of traits in each habitat under a migration--selection--mutation balance, compute the equilibrium values of the means, variances and asymmetries of the local distributions of phenotypes, and contrast the effects of migration and mutation on the evolutionary outcome. We then check our analytical results by solving our model numerically, and also assess their robustness in the presence of demographic stochasticity. While increased migration results in a decrease in local adaptation, mutation in our model does not influence the values of the local mean traits. Yet, both migration and mutation can have dramatic effects on population size and even lead to metapopulation extinction when selection is strong. Niche expansion, the ability for the population to adapt to both habitats, can also be prevented by small migration rates and a reduced evolutionary potential characterised by rare mutation events of small effects; but niche expansion is otherwise the most likely outcome. Although our results are derived under the assumption of clonal reproduction, we finally show and discuss the links between our model and previous quantitative genetics models., Usage notesDebarre-etal_2013_JEB_CodesZipped folder containing R and Mathematica codes.摘要：突变与基因流如何影响空间异质环境下的种群存续、生态位扩张与局部适应？本文针对两种频率均等的生境适应问题，构建种群动态与进化模型，弥合了不同理论框架间的研究鸿沟。定性而言，本模型可产生四类结果：(i) 种群全局灭绝；(ii) 仅适应单一生境；此外还可同时适应两种生境，对应(iii) 特化表型或(iv) 泛化表型；本文确定了各类平衡态的达成条件。我们推导了迁移-选择-突变平衡下各生境的局域密度与性状分布的新型解析近似解，计算了局域表型分布的均值、方差与不对称性的平衡值，并对比了迁移与突变对进化结果的影响。随后通过数值求解模型验证了解析结果，并评估了存在种群动态随机性时结果的稳健性。研究发现，迁移增强会降低局部适应水平，但本模型中的突变对局域平均性状值无影响。然而，迁移与突变均会对种群规模产生显著影响，在选择强度较高时甚至会导致集合种群（metapopulation）灭绝。生态位扩张，即种群适应两种生境的能力，也会因较低的迁移率与有限的进化潜力（以低频率、小效应突变事件为特征）受到阻碍；但在其他条件下，生态位扩张是最有可能出现的结果。尽管本文结果基于无性繁殖假设推导得出，我们最后还探讨了本模型与既往数量遗传学模型之间的关联。 使用说明：Debarre等人2013年发表于《Journal of Evolutionary Biology》（简称JEB）的配套代码压缩包，内含R语言与Mathematica语言代码。